In search of reliable backup and sync solution for Mac

I got several Macs to use, and need to have mostly same set of files on them.
I may not have some or all of them physically on the same location, so copying via LAN is not a solution.

I thought I found the solution: Amazon S3 + ExpanDisk + rsync + sparse image

(Ideally the solution should be Amazon S3 + s3fs + MacFUSE + rsync + sparse image, but latest s3fs requires new version of FUSE, while MacFUSE is in abandoned state, still using older FUSE)

BUT ... loading and accessing the image file over the net was painfully slow and unstable.